This research will seek to define the role of certain immunological phenomena in the establishment of experimental periodontal disease in gnotobiotic rats. The research plan has three major directions: (1) To determine if feeding a defined antigen to previously sensitized germfree rats will result in periodontal bone loss. (2) To characterize the gingival T and B cell response in germfree animals monoinfected with certain pathogenic organisms. (3) To determine the effects of induction of a specific salivary IgA antibody response on the establishment of periodontal bone loss in monoinfected gnotobiotic rats. A combination of immunological techniques will be employed in these investigations. Peripheral sensitization will be determined by lymphocyte transformation. T and B cells will be identified in intact gingival tissue and cell suspensions by specific fluoresceinated reagents. Serum and salivary antibody response will be determined by a radioactive antigen-binding technique.